The present invention relates to a process for preparing high purity hydrogen peroxide and more particularly to a process for safe and inexpensive preparation of hydrogen peroxide having purity higher than that of hydrogen peroxide obtained according to the prior art.
Recently, hydrogen peroxide has been used as a detergent for silicon wafer, etc. in the field of electronic industry, and with higher integration of IC there is an increasing demand for higher purity of hydrogen peroxide
Generally, in the case of hydrogen peroxide, the material of its manufacturing plant and storage equipment is corroded and dissolved out, resulting in that hydrogen peroxide is contaminated by metal ions. In this case, the kind of metal ions is different depending on the material of the equipment used. Hydrogen peroxide is contaminated by aluminum ion in the case where the material is aluminum, or it is contaminated by such metal ions as iron, chromium and nickel in the case where the material is stainless steel.
Since those impurities exert various bad influences on IC products, various purifying methods for removing them are under study.
Polish Patent Nos. 50,982 and 55,378, Spanish Patent No. 382, 719 and East German Patent No. 51,027 propose methods of removing metal ions contained in hydrogen perioxide by using a sulfonic acid type cation exchange resin in which a styrene-divinylbenzene copolymer is a matrix. However, even according to those proposed methods, there remain 10 ppb or so of metal ions in the hydrogen perioxide after treatment, thus not satisfying the users' demand in the field of electronic industry.
In the article "Chemical Marketing Reporter", Apr. 28, 1986, page 4, there is described a method of removing emulations from hydrogen peroxide in which hydrogen perioxide after distillation is re-distilled in a distillation equipment comprising a distillation tower made of borosilicate glass and a piping made of polyvinylidene fluoride. Even if hydrogen peroxide is purified by such method, the metal ion content is 0.1 ppm or less. Such a degree of purification for hydrogen-peroxide is insufficient.
As another method of removing metal ions contained in hydrogen peroxide, the present inventions have studied a treating method using metal chelate resins each having amidoxime, amino phosphoric acid or polyamine group in a resin matrix. However, none of such metal chelate resins afforded a satisfactory effect; besides, there is the disadvantage that the organic acid content of hydrogen peroxide increases. Thus, the said method proved to be inappropriate as a metal ion removing method.